Polyhydron make Prefill and Exhaust valves
are reliable hence require very little attention from user. However it is necessary that
following points must be kept in mind while storage, operation, commissioning and
maintenance.

Storage :

During storage take care that this valve is
properly covered and well lubricated. This will prevent ingress of dust and dirt in
working mechanism and during commissioning it will be easy to install the same.

Operation :

The Prefill and exhaust valves are designed
specifically to eliminate the need for high volume pumps on large press circuits.

Seat type construction.

Allows free flow from port A to port B.
Flow from port B to port A can be had by applying pilot pressure to its port X.

Decompression feature enables the valve to
open in two stages progressively allowing smooth and rapid exhaust of compressed oil.

The opening and closing of the valve can be
influenced by providing throttle cum check valve in port X.

Commissioning :

The things that should be attended to
during commissioning are as follows:

The port A should be connected to tank,
port B to pressure side and port X to the pilot pressure.

Cap screws and the corresponding tightening
torque should be as mentioned in the data sheet.

O' ring (supplied with the valve
separately) should first be fitted on the guide. The valve is then slowly and carefully
placed inside the cavity. This will ensure proper sealing of the valve.

Maintenance :

To enhance the proper working of the valve
it is necessary to attain the following points. :

The oil must be of prime quality and clean
as per ISO code 16/13.

Contaminated oil may lead to the wear of
the spool there by increasing clearance between the pilot piston and housing. This results
in the improper working of the valve.

The oil temperature must be within the
specified range i.e. -20 °C to +70 °C.